1. Field of the Invention
The invention is related to a flow valve or shut-off cock for flow networks with sealing means of particular features which make its design easy and increase its tightness and useful life.
2. Description of the Related Art
Several designs of flow valves are known, which have tried to simplify their manufacture and increase the tightness, but most of them loses their efficiency before working pressures higher than the normal ones. There are others, which, although reducing the number of components making up the valve (which facilitates the assembly of them), must make use of complex geometry which make die making more expensive.
A group of known valve designs, such as that under patent U.S. Pat. No. 3,974,869, consists in an elastic envelopment around a rigid stem which acts as the core of the system. The efficiency of these valves depends on the quality of the material with which the elastic component is manufactured, and makes it necessary a very accurate construction of the components in order to ensure a suitable fit among them and a low friction coefficient. Notwithstanding this, and due to the fact that the sealing means of these valves are independent from the flow pressure, the pressure exerted by the sealing means against the inner walls of the valve is constant and generates unnecessarily high friction forces, although flows with low pressures are controlled, which reduces their useful life. Another disadvantage of these valves is related to the restrictions caused by the election of materials of the valve body in order to ensure that their coefficient of thermal expansion be lower than the coefficient of thermal expansion of the sealing elements.
Another type of valve known is that under patent U.S. Pat No. 3,814,120, which is very complex due to the number and shape of its components. The quality of the sealing effect is constant, showing problems at high pressure ranges.
The sealing elements of the known valves mainly act on a measure exceeding the same with respect to the sizes of the valve body, the compression forces of the sealing material being those which exercise the sealing function itself. According to this, these designs of valve demand the existence of an element of inner rigid stem in the sealing element acting as supporter.